Corrosion inhibited lubricating composition



United States Patent O "ice 3,278,427 CORROSKON ENHEBITED LUBRICATINGCOMPOSITION Richard A. Butcosk, Westmont, N..l'., assignor to Mobil OilCorporation, a corporation of New York No Drawing. Filed Oct. 28, 1963,Ser. No. 319,497 13 Claims. (Cl. 252-25) This invention relates tolubricating compositions suitable for use over a wide range of operatingconditions. In one of its aspects, the invention relates to lubricatingcompositions containing certain materials which exhibit corrosion orrust-inhibiting characteristics when incorporated in these compositions.Still more particularly, in this aspect, the invention relates tolubricating grease compositions exhibiting the aforementionedcorrosion-inhibiting characteristics, and to a method for theirpreparation.

In the preparation of lubricating compositions, as for example, greasesand other lubricants of varying viscosities, it has been the practice toincorporate in these compositions various corrosion or rust-inhibitingmaterials to avoid the deleterious effect upon metal surfaces beinglubricated, when such surfaces are continuously or intermittentlysubjected to humid or wet environmental conditions. Among thecorrosion-inhibiting materials that have been suggested for this purposeare the alkali metal nitrites, which are well known for theircorrosion-inhibiting properties. Of particular importance, in thisrespect, is sodium nitrite. In general, it has been found that in orderto achieve a fairly adequate degree of corrosion-inhibiting effect inthe aforementioned lubricating compositions, the alkali metal nitriteshould be employed in the lubricant in an amount equal to at least about2 percent, by weight, of the total lubricating composition. In thisrespect, however, it has also been found that the presence of even suchlow concentrations of alkali metal nitrite results in the abrasion anddeterioration of the metal surfaces being lubricated by the grease orother lubricating composition. On the other hand, the use of lowerconcentrations of the alkali metal nitrite in the lubricant, does notresult in imparting suflicient corrosion-resistant properties to thelatter. Thus, prior to the present invention no effective and relativelysimple method has been proposed for the incorporation of alkali metalnitrites in lubricating compositions in relatively small concentrationsand which, nevertheless, still impart adequate corrosion-resistantproperties to the lubricant.

It is, therefore, an object of the present invention to provide improvedcorrosion-inhibiting materials for lubricating compositions.

Another object of the invention is to provide improvedcorrosion-inhibiting materials, comprising alkali metal nitrites, forlubricating compositions.

Still another object of the invention is to provide lubricatingcompositions having improved corrosion-inhibiting properties, andwherein metallic surfaces being lubricated by these compositions are notsignificantly abraded or otherwise damaged.

A still further object of the invention i to provide a method forpreparing the aforementioned lubricating compositions.

Other objects and advantages inherent in the invention will becomeapparent to those skilled in the art from the following description.

It has now been found that lubricating compositions having effective anduseful corrosion and rust-inhibiting properties may be preparedemploying relatively small amounts of alkali metal nitrites, as theinhibitors, when used in conjunction with aN-carboxymethyl-alkenyl-succinamic acid, as more fully hereinafterdescribed. The synergistic effect of this additive combination makes it?atented Oct. 11, 1966 possible to employ such small quantities of thealkali metal nitrite and the N-carboxymethyl-alkenyl-succinamic acidsthat metallic surfaces being lubricated are not abraded or otherwisedamaged by the nitrite components in the lubricating composition.Furthermore, it has also been found that this ability of the lubricatingcomposition to exhibit effective corrosion-inhibiting properties,although employing relatively small amounts of the nitrite component,could not otherwise be achieved except for the presence, and thesynergistic effect, of the N-carboxymethyl-alkenyl-succinamic acidcomponent.

Insofar as the components comprising the corrosion inhibitor areconcerned, the alkali metal nitrites which may be employed includesodium nitrite, potassium nitrite and lithium nitrite. Of these, sodiumnitrite is preferred. The alkali metal nitrite is generally employed inthe inhibitor composition in an amount from about 40 to about 70percent, by weight, and preferably in an amount from about 45 to about65 percent, by weight, of the total inhibitor composition.

As indicated above, a N-carboxymethyl-alkenyl-succinamic acid isemployed in conjunction with the alkali metal nitrite in the inhibitorcomposition for its synergistic effect. These succinamic acids can beprepared by several methods known to those skilled in the art. Ingeneral, they can be prepared by reacting an alkenyl succinic acidanhydride or an alkenyl succinic acid with glycine (aminoacetic acid),in equimolar amounts and with the elimination of water of condensation,when the acid is employed. Accordingly, the reaction will be carried outat temperatures of between about C. and about C. The time of reactionwill be dependent, of course, upon the reaction temperature employed.Reaction will take place readily when the acid anhydride is employed.When the acid is employed, reaction will continue until the requiredamount of water of condensation has evolved. Generally, the time willvary between about 6 to about 10 hours, and shorter reaction times arerequired if water is removed by azeotropic distillation. Suitableliquids which form azeotropes with water are non-polar solvents, such asbenzene, toluene, and xylene.

The alkenyl succinic acid anhydride reactant can, generally, have fromabout 8 to about 35 carbon atoms in the alkenyl radical, particularlywhen employed in grease compositions, and preferably from about 10 toabout 14 carbon atoms. Non-limiting examples of the alkenyl succinicacid anhydride reactants are octenyl succinic acid anhydride,diisobutenyl succinic acid anhydride, Z-methylheptenyl succinic acidanhydride, 4-ethylhexenyl-succinic acid anhydride, nonenyl succinic acidanhydride, decenyl succinic acid anhydride, undecenyl succinic acidanhydride, dodecenyl succinic acid anhydride, triisobutenyl succinicacid anhydride, tetrapropenyl succinic acid anhydride, tetradecenylsuccinic acid anhydride, hexadecenyl succinic acid anhydride,ll-tricosenyl succinic anhydride, and l7-pentatriacontenyl succinicanhydride. As mentioned hereinbefore, the alkenyl succinic acidscorresponding to these alkenyl succinic acid anhydrides can also be usedto prepare the succinamic acids employed in the inhibitor composition.The preparation of the aforementioned N-carboxymethyl-alkenyl-succinamicacids is more fully discussed in US. Patent No. 3,039,861, issued June19, 1962. The N-carboxymethyl-alkenyl-succinamic acid is generallyemployed in the inhibitor composition in an amount from about 30 toabout 60 percent, by weight, and preferably in an amount from about 35to about 55 percent, by weight, of the total inhibitor composition.

The quantity of the corrosion inhibitor employed will depend upon thecharacteristics of the lubricating composition being treated and thenature of the environmental conditions encountered by the lubrioant inperforming its function. In general, the more viscous types oflubricating compositions, for example, those which are normallyclassified as greases, may contain the aforementioned inhibitors whichcomprise from about 0.2 to about 3.0 percent, by weight, and,preferably, from about 0.5 to about 1.5 percent, by weight, of the totallubricant composition. The amount of alkali metal nitrite present maycomprise from about 0.1 to about 2.0 percent, by weight, and,preferably, from about 0.3 to about 1.0 percent, by weight, of the totallubricant composition. The amount of N -carboxymethyl-alkenyl-succinamicacid present may comprise from about 0.1 to about 1.0 percent, byweight, and preferably, from about 0.2 to about 0.5 percent, by weight,of the total lubricant composition.

In preparing the improved lubricants containing the novel inhibitorcompositions of the present invention, the manner in which the alkalimetal nitrite and the N-carboxymethyl-alkenyl-succinamic acid areincorporated into the lubricant is critical with respect to the state ofthe individual inhibitor components employed. Thus, if the alkali metalnitrite and the N-carboxymethyl-alkenylsuccinamic acid are to be addedto the lubricant under substantially anhydrous conditions, i.e. eitheras solids or in the presence of a non-aqueous vehicle for one or both ofthe components (e.g. mineral oils, alcohols, etc.), these components maybe incorporated into the lubricant either separately, and in anysequence; or they may first be admixed, and thereafter, the thus-formedinhibitor composition may be incorporated therein. If, on the otherhand, the aforementioned inhibitor components are added under aqueousconditions, it is essential that the aqueous nitrite component be firstincorporated into the lubricant while the latter is maintained at anelevated temperature sufficient to drive off water present, and thesuccinamic acid is thereafter added. This sequence is necessitatedbecause of the fact that if the succinamic acid were first incorporatedinto the lubricant, the succinamic acid being reactively acid wouldcause the nitrite to decompose and liberate nitrous oxide under theaqueous conditions present, thereby rendering the nitrite componentineffective as a corrosion inhibitor and also bring about corrosion ofmetal surfaces being lubricated.

The following examples will serve to illustrate the preparation oftypical improved corrosion inhibitor compositions of the presentinvention, and their incorporation and performance in lubricantcompositions. In the examples, where indicated, sodium nitrite andN-carboxymethyl-tetrapropenyl-succinamic acid (comprising the reactionproduct of glycine with tetrapropenyl succinic anhydride) wereincorporated into a calcium lead-acetate complex grease prepared inaccordance with the procedure described in US. Patent 2,898,297, issuedAugust 4, 1959. In each instance aqueous solutions of sodium nitritewere employed and were added to the grease, While the latter wasmaintained at a temperature of about 210 F. and for a period of timesufiicient to drive off the water present. The succinamic acid wasthereafter added. The respective grease formulations were next subjectedto the Bearing Protection Test, ASTM D-1743 rating, with the respectiveratings, in each instance, being recorded, as shown.

.#1 ratingno spots on bearing case or on roller (excellent). #2 rating-1to 3 very small spots (fair). #3 mting3 or more large spots (poor).

, From the above data, it will be seen, as shown in Examples 5 and 6,that a synergistic effect is obtained by the combined use of the alkalimetal nitrite, as exemplified by sodium nitrite and theN-carboxymethyl-alkenylsuccinamic acid, as exemplified byN-carboxymethyl-tetrapropenyl-succinamic acid, when compared to the useof each of these components, alone, as shown in Examples 2, 3 and 4, orin their absence, as shown in Examplel It will be understood, of course,that other alkali metal nitrites may be substituted for the sodiumnitrite, and that other N-carboxymethyl-alkenyl-succinamic acids may besubstituted for the N-oarboxymethyl-tetrapropenyl-succinamic acid, asshown in the above examples, and that corrosion inhibitors containingthese components may be incorporated in a wide variety of lubricantcompositions.

While preferred embodiments of the compositions of the present inventionand the process for their preparation have been described for thepurpose of illustration, it should be understood that variousmodifications and adaptations thereof, which will be obvious to thoseskilled in the art, may be made without departing from the spirit of theinvention.

I claim:

1. A lubricant composition containing a corrosion inhibitor, saidinhibitor consisting essentally of an alkali metal nitrite and aN-carboxymethyl-alkenyl-succinamic acid containing from about 8 carbonatoms to about 35 carbon atoms in the alkenyl group thereof.

2. A grease composition containing a corrosion inhibitor, said inhibitorconsisting essentially of an alkali metal nitrite and aN-carboxymethyl-alkenyl-succinamic acid containing from about 8 carbonatoms to about 35 carbon atoms in the alkenyl group thereof.

3. A grease composition containing a corrosion inhibitor, said inhibitorconsisting essentially of an alkali metal nitrite and aN-carboxymethyl-alkenyl-succinamic acid containing from about 10 carbonatoms to about 14 carbon atoms in the alkenyl group thereof.

4. A grease composition containing a corrosion inhibitor, said inhibitorconsisting essentially of sodium nitrite andN-carboxymethyl-tetrapropenyl-succinamic acid.

5. A grease composition containing from about 0.2 to about 3.0 percent,by weight, of the grease, of a corrosion inhibitor consistingessentially of from about 40 to about 70 percent, by weight, ofan alkalimetal nitrite and from about 30 to about 60 percent, by weight, of a Ncarboxymethyl alkenyl succinamic acid containing from about 8 carbonatoms to about 35 carbon atoms in the alkenyl group thereof.

6. A grease composition containing from about 0.5 to about 1.5 percent,by weight, of the grease, of a corrosion inhibitor consistingessentially of from about 45 to about 65 percent, by weight, of analkali metal nitrite and from about 35 to about 55 percent, by weight,of a N-carboxymethyl-alkenyl-succinamic acid containing from about 10carbon atoms to about 14 carbon atoms in the alkenyl group thereof.

7. A composition consisting essentially of an alkali metal nitrite and aN-carboxymethyl-alkenyl-succinamic acid containing from about 8 carbonatoms to about 35 carbon atoms in the alkenyl group thereof.

8. A composition consisting essentially of an alkali metal nitrite and aN-carboxymethyl-alkenyl-succinarnic acid containing from about 10 carbonatoms to about 14 carbon atoms in the alkenyl group thereof.

9. A composition consisting essentially of from about 40 to about 70percent, by weight, of an alkali met-a1 nitrite and from about 30 toabout 60 percent, by Weight, of a N-carboxymethyl-alkenyl-succinamicacid containing from about 8 carbon atoms to about 35 carbon atoms inthe alkenyl group thereof.

10. A composition consisting essentially of from about 45 ltO about 65percent, by weight, of an alkali metal nitrite and from about 35 toabout 55 percent, by weight, of a N-carboxymethyl-alkenyl-succinamicacid containing from about carbon atoms to about 14 carbon atoms in thealkenyl group thereof.

11. A composition consisting essentially of sodium nitrite andN-carboxymethyl-tetrapropenyl-succinamic acid.

12. A composition consisting essentially of from about to about 70percent, by Weight, of sodium nitrite and from about 30 to about 60percent, by Weight, of N-carboxymethyl-tetrapropenyl-succinamic acid.

13. A composition consisting essentially of from about to about 65percent, by weight, of sodium nitrite and from about 35 to aboutpercent, by Weight, of N-carboxymethyl-tetrapropenyl-succinamic acid.

References Cited by the Examiner UNITED STATES PATENTS 3,039,861 6/1962Andress et al. 4471 5 3,089,848 5/1963 Morway 252-25 X FOREIGN PATENTS892,266 3/1962 Great Britain.

10 DANIEL E. WYMAN, Primary Examiner.

P. P. GARVIN, Assistant Examiner.

1. A LUBRICANT COMPOSITION CONTAINING A CORROSION INHIBITOR, SAIDINHIBITOR CONSISTING ESSENTIALLY OF AN ALKALI METAL NITRITE AND AN-CARBOXYMETHYL-ALKENYL-SUCCINAMIC ACID CONTAINING FROM ABOUT 8 CARBONATOMS TO ABOUT 35 CARBON ATOMS IN THE ALKENYL GROUP THEREOF.